With only 501 miles on it you will not need rings yet. I have 3500 miles on my 04 and the rings are lilke new. Unless you have super light powder in Alaska, the stock 151 x 16 x 2 track will do just fine. If you port the stock track it will help keep snow from building up inside the rear suspension. I run two 2" holes down the middle of the track which gets the job done.
BJ- wanna bet...YOU need new pistons before next season..the moly rings fail easily in 200 miles (done it)
If a taller light weight seat that has a ton of storage is important consider an AXESS seat. The top of the seat is narrow and does not get in the way of swinging you leg over. I have had Boss seats in the past and the AXESS is better in every way except it is not as stylish. But I carry an extra belt, a Snobungie, first aid kit, extra gloves and goggles and trail bars under the seat top.
www.rmproducts.info
BJ- any seat is better than stock, go taller with storage you will be fine unless your shorter fella...
One of the best mods I did was to convert my running boards to SnoEliminators which not only keep the boards snow free but stiffen up the running boards.
BJ- 2005's have new/better boards than the 2004
SLP makes a good can that is not louder than stock. If you ceramic coat the pipe you can save about 12# of weight and have a better running sled. The AXCESS seat will save another 6#, the sway bar another 4#, boggie wheels another 3-4#, clutch guard and engine foam another 3-4# for about a 30# weight reduction.
Trash the skis. I currently ride on Simmons but am seriously considering Sly Dogs for next year.
BJ- stock are bad...the newer pilot 6.9's work well, find a new take off set??
Dynamo^Joe has a clutch kit that, once dial in, will really make that sled perform. Check out
www.dootalk.com Lots of good DOO info on that site.
So far I see no reason for me to go to a newer sled as mine has no trouble keeping up with 07s and a few stock XPs.
Have fun with the project, the REV is a totally different ride than the CATS but after a few days on the sled you'll never look back.
BCB